The invention relates to an arbitration circuit. More particularly, the invention relates to a preemptive round robin arbitration circuit.
When an asset or resource, such as a personal computer data bus, needs to be used by multiple requesters, such as a modem, a hard disk and/or a software program, some kind of allocation scheme needs to be provided. Hence, if no single asset or resource is in an extreme hurry, a round robin scheme may be used where, on a given clock cycle, one device request line is polled to ascertain whether or not that requester or device has a need for the asset. If there is a request, the request is granted for an appropriate amount of time. After that request is removed or finished, the system proceeds to the next requester in line. If a device far down the line of requesters in the round robin circuit has a request even though no one else has a request between the present arbitration logic circuit and the one connected to a requester requiring access to the asset, the circuit may still require one or more clocks to get to the requester having a present need to acquire the use of the asset. Therefore, overhead for the conventional round robin circuit may take more than one cycle when the service is granted from one request to another request. Furthermore, the circuit may not allow an interactive request to break in during a granted batch request if both batch request and interactive request are asserted resulting in the response time to the interactive request to become intolerable. The interactive request is an asynchronous request typically containing control information, whereas the batch request is a synchronous request typically involving sequentially accessed data.
In some cases, conventional resource allocation schemes use a priority interrupt technique where the requester with the most priority is always the next one to have access to the asset. However, with such a priority interrupt technique, a requester with low priority may have to wait an extremely long time before being granted access to an asset.